Pasteurized in-shell chicken eggs and method for production thereof

ABSTRACT

A method of pasteurizing in-shell chicken eggs by heating eggs until a central portion of the yolks of the eggs is at a temperature between 128° F. to 138.5° F. That temperature is maintained and controlled for times within parameter line A and parameter line B of FIG.  1  and sufficient that any Salmonella species present in the yolk is reduced by at least 5 logs but insufficient that an albumen functionality of the egg measured in Haugh units is substantially less than the albumen functionality of a corresponding unpasteurized in-shell egg.

[0001] The present invention relates to pasteurized in-shell chickeneggs and to a method for production thereof, and, more particularly, tosuch eggs and method where certain pathogens whenever present in theeggs are reduced in quantity to a level safe for human consumption whileat the same time the functionality of the eggs is preserved,particularly the albumen functionality, such that the pasteurized eggsare substitutable for fresh, unpasteurized eggs in most consumptionuses.

BACKGROUND OF THE INVENTION

[0002] The term pasteurization is used herein in connection with thepresent invention in the general sense that the term is applied to otherfood products, e.g. pasteurized milk, in that the present pasteurizedeggs are partially sterilized at temperatures which destroyobjectionable microorganisms, without major changes in the functionalityof the eggs. In this regard, food products are conventionally heated attemperatures and for times so as to sufficiently destroy pathogenicmicroorganisms, which may be contained in the food, so that thepasteurized food is safe for human consumption. In order to provide apasteurized food safe for human consumption, it is not necessary thatall pathogenic microorganisms in the food be destroyed, but it isnecessary that those pathogenic microorganisms be reduced to such a lowlevel that the organisms cannot produce illness in humans of usualhealth and condition. For example, fresh whole milk may contain virulentpathogenic microorganisms, most notably microorganisms which causetuberculosis in humans, and during pasteurization of the milk, thosepathogenic microorganisms are reduced to such low levels that the milkis safe for consumption by humans of ordinary health and condition. Inthe case of some microorganisms, however, usual pasteurizationtemperatures and times can completely destroy those microorganisms. Milkso pasteurized does not have major changes in the functionality thereof.The taste and texture of pasteurized milk is slightly changed, but thosechanges are not of practical significance to most consumers thereof.

[0003] Heat destruction of microorganisms in eggs has long been known inthat the eggs were cooked sufficiently to effect destruction thereof.For example, when frying an egg, fried to a reasonable hardness,microorganism destruction will occur. Likewise, when boiling an egg to ahard-boiled state, heat destruction of microorganisms in the egg willoccur. However, with these cooking processes, major changes in thefunctionality of the egg occurs, e.g. coagulation of the yolk and white,and, thus, this is not pasteurization in the usual sense, as explainedabove.

[0004] Recently, pasteurization of liquid chicken eggs (eggs out of theshell) has been commercially practiced. The process, very basically,involves heating liquid chicken eggs for short times at highertemperatures to reduce any pathogenic microorganisms therein such thatthe pasteurized liquid chicken eggs are safe for human consumption,while, at the same time, major changes in functionality do not occur.See, for example, U.S. Pat. No. 4,808,425.

[0005] However, the art has long since struggled with pasteurizingin-shell chicken eggs. While in-shell eggs may be heated sufficiently todestroy microorganisms, the art has not, at the same time, been able tosubstantially retain the functionality of the eggs. The functionality isdetermined by various tests, but a more basic test is that of thealbumen functionality, which test measures the whipped volume, understandard conditions, of whipped liquid albumen, as measured in Haughunits.

[0006] In the case of liquid chicken eggs (not in the shell), by carefulcontrol of the time and temperature of heating the liquid eggs, usuallywith a short time, high temperature (HTST) apparatus, pasteurization canbe achieved while retaining, at least substantially, the functionalityof the eggs. This is particularly true when the liquid eggs are heatedfor pasteurization purposes in a very thin film, where the temperatureand time of heating of the liquid eggs can be very carefully controlled.

[0007] In liquid eggs, the yolk may or may not be mixed with thealbumen. As can be appreciated, however, with in-shell chicken eggs(also referred to as “shell eggs”), not only is the mass of the eggsubstantially different from the mass of a unit of thin film of liquideggs, but the yolk is essentially centrally positioned in the shell.Accordingly, while the art has struggled for some time to carefullycontrol temperatures and times for pasteurizing in-shell eggs, none ofthose efforts in the art have been successful in terms of both reducingpathogenic microorganisms found in chicken eggs to a level safe forhuman consumption while maintaining essentially the same functionalityof the eggs as unpasteurized eggs. As a result, no commercial processfor pasteurizing in-shell eggs and no commercial pasteurized in-shelleggs have been available.

[0008] The art has taken many different approaches in attempts topasteurize in-shell eggs. See, for example, U.S. Pat. Nos. 1,163,873;2,423,233; 2,673,160; and 3,658,558. The more prevalent approachesinvolve heating the in-shell eggs, usually in a water bath, for varioustimes and at various temperatures, as specified by the variousinvestigators in the art. These times and temperatures specified by thevarious investigators vary widely, and this is because all of thoseapproaches involve a compromise either in the degree of safety achievedor in the quality of the functionality retained.

[0009] In this latter regard, if the in-shell egg is heated in a waterbath, where the water bath temperature and time of heating are specifiedby the investigator, one of two results have generally occurred. Thefirst result is that, when higher temperatures and longer times arespecified, while the egg may be acceptably reduced in microorganismcontent, the functionality of the egg is also considerably reduced, suchthat the egg is no longer substitutable for unpasteurized eggs in eitherusual home cooking, e.g. frying, or in conventional baking recipes. Theother result, when using lower temperatures of the water bath andshorter times, while the functionality of the egg is substantiallymaintained, the decrease in pathogenic microorganisms, which may bepresent in the eggs, is severely compromised, and the egg may be saferbut not be safe for human consumption. While eggs processed according tothis latter approach can be said to be safer to eat, in that there issome reduction of pathogenic microorganisms in the eggs, the eggs arenot pasteurized in the sense as set forth above, i.e. that they are safefor consumption by humans of ordinary health and condition.

[0010] Faced with the above difficulties, that art searched forintermediate water bath temperatures and dwell times where functionalityof the egg is preserved and microorganisms are substantially reduced.Unfortunately, these searches have generally resulted in the worst ofboth of the results noted above, i.e. both reduced functionality of theegg and still insufficient reduction in microorganisms, which result isless desirable than either of the two above-noted general results.

[0011] Accordingly, therefore, the art has been on the horns of adilemma, i.e. if the times of dwell and temperatures of the water bathare high enough to substantially reduce the microorganism content ofin-shell eggs, then the functionality of the eggs is substantiallyreduced, while if the times of dwell and temperatures of the water bathare sufficiently low as to substantially maintain the functionality ofthe eggs, the eggs are not sufficiently reduced in microorganism contentso as to be pasteurized.

[0012] Pathogenic microorganisms are introduced into chicken eggs by twoprincipal routes. Firstly, pathogens are introduced into the in-shelleggs from environmental contamination. This environmental contaminationmay occur through a variety of causes, but typically, infected chickensor mice in commercial egg-laying chicken houses deposit feces whichcontact the shell of a laid egg. Certain microorganisms, especiallySalmonella, when in contact with the shell of the egg, can penetratethat shell, especially through small fissures or pores in the shell.That contamination is, therefore, from the outside of the shell into theegg, and the contamination remains, largely, in the albumen near theshell. This contamination can be very substantially reduced by theabove-noted approaches of the prior art, since, when the egg is placedin a water bath heated to the temperatures suggested by the art, this issufficient to heat the albumen near the shell and substantially destroypathogens which may have penetrated the shell from environmentalcontamination. In this sense, the egg is, indeed, safer to eat.

[0013] The second route of contamination in the eggs is systemic, andthis poses a far more difficult problem. Typically, feces of infectedchickens or mice are ingested by the chicken during feeding, and thatinfection becomes systemic in the chicken. Certain organisms, verynotably Salmonella enteritidis, enter the bloodstream of the chicken andpass, trans-ovarially, into the interior of the egg itself. Mostespecially, that systemic contamination occurs in the yolk of the egg,although that contamination can also easily extend into the albumen. Inthis type of contamination, the prior art approaches, as noted above,are ineffective toward substantially reducing microorganisms in theeggs, including the yolk, while at the same time maintaining thefunctionality of the eggs.

[0014] While many suggestions have been made in the prior art,principally, a water bath is heated to specified temperatures (althoughair, oil and the like heat transfer media have been suggested), and thein-shell eggs are then placed in that heated water bath and dwelltherein for a specified length of time. It is generally assumed that theyolk temperature will come to equilibrium with the water bathtemperature after a sufficiently long dwell time of the eggs.Unfortunately, specifying the temperature of the water bath and the timeof dwell of the eggs therein does not necessarily specify temperatureswithin the eggs, and especially the yolks. This is because eggs can varyin one or more of weight, size, shape, composition (e.g. relative sizeof yolk and air sack) and density, all of which affects the heattransfer properties of a particular egg in the water bath at thespecified temperatures. Thus, when operating in water baths at specifiedtemperatures within specified time ranges, the temperature within aparticular egg, and especially the yolk, is entirely problematic, and,hence, the control of the prior art approaches toward pasteurizing eggs,especially in regard to yolk contamination, has been completelyinadequate and more or less is a matter of chance—see, for example, WO95/14388.

[0015] The specified temperatures of the water baths in the prior artvary considerably, with some investigators taking the approach ofrelatively low temperature baths, e.g. as low as about 100° F., withlong dwell periods of the eggs, while other investigators took theapproach of high temperature baths, e.g. up to 160° F., with relativelyshort dwell periods of the eggs, and others took an intermediateapproach, e.g. 130° F. to 140° F., with intermediate dwell periods, e.g.50 minutes. However, no matter which of these approaches is adopted, asexplained above, the art simply has not found combinations oftemperatures of water baths and times of dwell which will ensure eggssafe for human consumption, i.e. pasteurized eggs, includingpasteurization of the yolks, while at the same time maintaining thefunctionality of the eggs. Accordingly, it would be a very substantialbenefit to the art to provide a method for pasteurizing eggs where theeggs are not only pasteurized, i.e. safe for consumption by humans ofordinary health and condition, but which also assures that thefunctionality of the eggs is substantially retained.

BRIEF SUMMARY OF THE INVENTION

[0016] Very briefly, the present invention provides pasteurization of anin-shell chicken egg, i.e. safe to eat by humans of ordinary health andcondition, by achieving a 5 log reduction of Salmonella species whichmay be present in the egg by controlling the yolk temperature withinrelatively narrow limits so that both the pasteurization is achieved andthe functionality of the egg is not substantially decreased. In theseregards, the present invention is based on several primary discoveriesand several subsidiary discoveries.

[0017] As a primary discovery, it was found that, if the temperature anddwell time of the yolk is at a certain correlation of temperature andtime or within a 95% confidence level deviation, Salmonella specieswhich may be present in the egg yolk, as well as the albumen, can bereduced by at least 5 logs, which reduction is sufficient for truepasteurization, i.e. safe for consumption by humans of ordinary healthand condition, while at the same time there is a retention offunctionality of the eggs.

[0018] As a subsidiary discovery in this regard, it was found that, ifSalmonella species are reduced by that at least 5 logs, othermicroorganisms found in the egg are also reduced, such that the egg ispasteurized in respect to those other microorganisms.

[0019] As a second primary discovery, it was found that, if the egg ispasteurized according to that certain correlation, or within the limitsof deviations noted above, the albumen functionality of the egg,measured in Haugh units, is not substantially deteriorated, as comparedwith a corresponding unpasteurized in-shell egg.

[0020] As a third primary discovery, it was found that, in order toeffectively pasteurize an egg, the yolk temperature of that egg must becontrolled within relatively narrow temperature limits.

[0021] As a subsidiary discovery in this regard, it was found that thetemperature of the yolk must be controlled in a range of from 128° F. to138.5° F. At temperatures of the yolk below 128° F., adequatepasteurization will not occur. On the other hand, at temperatures of theyolk above 138.5° F., the functionality of the egg substantiallydecreases.

[0022] As a fourth primary discovery, it was found that, within thisrange of yolk temperatures, the dwell time of the yolk at a selectedtemperature must be relatively closely correlated to that temperature.If the dwell time is significantly below that correlation,pasteurization will not occur. On the other hand, if the dwell time issignificantly above that correlation, then the functionality of the eggis substantially deteriorated.

[0023] As a subsidiary discovery in this regard, it was found that thelimits of deviation from that correlation which are permissible toachieve both pasteurization and retention of functionality arerelatively small. Deviations should be no greater than that which willprovide a 95% statistical confidence level of pasteurization. Thus, thelimits of deviation from that specific correlation must be carefullyobserved.

[0024] Thus, broadly stated, the present invention provides a method ofpasteurizing an in-shell chicken egg comprising heating the egg until acentral portion of the yolk of the egg is controlled within the range of128° F. to 138.5° F., and maintaining that controlled yolk temperaturefor times within parameter line A and parameter line B of FIG. 1 annexedhereto and sufficient that a Salmonella species that may be present inthe egg is reduced in amount by at least 5 logs but insufficient that analbumen functionality of the egg measured in Haugh units issubstantially less than the albumen functionality of a correspondingunpasteurized in-shell egg.

[0025] The invention also provides a pasteurized in-shell chicken eggcomprising a pasteurized central portion of a yolk of the egg having atleast a 5 log reduction of a Salmonella species that may be present inthe yolk in its unpasteurized form. The so-pasteurized egg will have analbumen functionality measured in Haugh units not substantially lessthat the albumen functionality of a corresponding unpasteurized in-shellegg.

BRIEF DESCRIPTION OF THE DRAWING

[0026]FIG. 1 is a graph showing the required correlation between thetemperatures of a central portion of the yolk of an egg during thepasteurization process and the log (base 10) of time at which thatcentral portion of the yolk of the egg dwells at such temperatures. Thatgraph also shows permissible limits of deviation from that correlation,indicated by parameter lines A and B.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0027] The present invention is directed to in-shell chicken eggs, andit cannot be extrapolated to other in-shell poultry eggs. In-shellpoultry eggs from different birds vary considerably in the mass,propensity for coagulation of the albumen and yolk, temperatures anddwell times for adequate pasteurization, heat transfer properties, andusual functionalities. For example, it has been found that an in-shellduck egg, which is probably the closest poultry egg to a chicken egg,cannot be pasteurized to a 5 log cycle reduction of a Salmonella speciesfound in chicken eggs and maintain functionality with the method of thepresent invention. In attempts to pasteurize in-shell duck eggs by thismethod, it was found that the time and temperature correlations foundfor in-shell chicken eggs were inappropriate for in-shell duck eggs.Therefore, it is emphasized that the invention relates only to in-shellchicken eggs, and the method of the invention cannot be consideredworkable to any other in-shell poultry egg. See Dutch Patent No. 72,454.

[0028] As opposed to the prior art, briefly summarized above, whichrelied upon the temperature of the medium for heating the egg, e.g.usually water, the present invention relies upon the temperatures of theyolk of the egg, along with the correlated dwell times of the yolk atthose temperatures, and for this reason, the particular medium in-whichthe egg is heated is not critical, as opposed to that of the prior art.Thus, in the prior art, since, generally speaking, the temperature ofthe heating medium was controlled and the temperature of the yolk wasessentially uncontrolled, the choice of heating medium was a criticalchoice because the heat transfer properties of a particular mediumgreatly influenced the results of the process. For that reason, most ofthe approaches in the prior art chose water as the heating medium, sincethe temperature of the water in a heating bath could be carefullycontrolled, and heat transfer from the water bath to the egg isaccelerated. The present invention does not rely on controlling thetemperature of the heating medium to effect pasteurization. Conversely,the present invention relies on controlling the temperature of the yolk.Thus, the heating medium of the present invention can vary widely. Theegg can be heated with any fluid heat transfer medium or it can beheated by direct heat from heat sources, such as radiant heaters,infrared heaters, or radiation, such as microwaves. However, since allof those direct heating means require special care in ensuring that thedirect heat uniformly heats all surfaces of the egg, it is preferredthat the heating medium is a fluid heat transfer medium, since the fluidcan be caused to flow around the egg and ensure uniform heating alongall surfaces of the shell of the egg. The fluid medium may be any gas,e.g. air, nitrogen, carbon dioxide, etc., but it is preferred that thefluid medium be an aqueous medium, since heat transfer from aqueousmediums is easy to control. Thus, the aqueous medium may be in the formof water vapor, but, more preferably, the aqueous medium is liquidwater. Mixtures or sequences of heating medium may also be used, e.g.water and then air.

[0029] However, liquid water does have a disadvantage in that, as iswell known, during heating in liquid water, gases nucleate on the shellof the egg. This can be observed by anyone boiling an egg in a pot. Thenucleated gases decrease the heat transfer between the liquid water andthe shell of the egg and, hence, into the interior of the egg. Sincethis decrease in heat transfer may not be uniform throughout the area ofnucleated gases on the shell of the egg, it is most preferable to avoidor displace those nucleated gases to the extent possible. This may bedone by adding a surface active agent to the water, e.g. a food-gradeionic, anionic or non-ionic surface active agent, many of which areknown in the art, for example, the Tweens. Usually only a fraction of apercent of surface active agent is necessary, e.g. one half of onepercent based on the weight of the water, although the surface activeagent can be as low as one hundredth of a percent and as high as threeor four percent.

[0030] Alternatively, the nucleated gases may be displaced from theshell of the egg when at least one of the water and the egg is in motionrelative to the other. Thus, the water may be sprayed onto the egg,which keeps the water in motion relative to the egg, or the egg may passthrough a substantially continuous curtain of flowing water, or in awater bath, the water may be fully circulated over the egg. In addition,in any of the above cases, the egg may be rotated on a support, andsupports for rotating eggs are well known in the art. Alternatively,both motion of the water and the egg can be used, along with asurfactant (non-foaming surfactant) to minimize or avoid inconsistentheat transfers due to nucleated gases.

[0031] As noted above, the present invention relies on controlling thetemperature and dwell time of the yolk of the egg. However, within theentire yolk, the temperatures thereof may vary, depending upon theproximity of a particular portion of the yolk to the shell and theproximity of the particular portion of the yolk to the center of theyolk. As will be explained hereinafter in detail, the present method iscarried out by controlling the temperature of the yolk at a centralportion thereof. The center of the yolk, of course, is a theoreticalpoint and modern temperature-measuring devices are not capable ofmeasuring temperatures at a theoretical point. However, such devices arecapable of measuring temperatures in a central portion of the yolk,consistent with the width of a modern temperature-measuring probe, e.g.thermocouple. Thus, in the present specification and claims, the centralportion of the yolk is defined to mean that portion of the yolksubstantially surrounding the center of the yolk which has sufficientvolume to accommodate and receive a conventional temperature-measuringprobe.

[0032] As noted above, it has been found that the temperature of theyolk must be in the range of 128° F. to 138.5° F. While pasteurizationcan be achieved with yolk temperatures as low as 126° F., thistemperature is near the minimum temperature to kill Salmonella andvariables, such as particular egg histories and sizes/grades, etc., asexplained below, very significantly affect results. Thus, at 126° F.,the results are so variable as to be unreliable, and to avoid the same,the yolk temperature must be at a higher value, i.e. at 128° F. orhigher.

[0033] In this regard, experiments which attempted to establish thecorrelation line of FIG. 1 at between 128° F. and 126° F. showed thedata for that correlation line to be so scattered that parameter lines Aand B could not be established with any certainty. This reflects that attemperatures below 128° F. the above-mentioned variables become sosignificant that pasteurization while retaining functionality cannot beaccurately predicted. Thus, for practical application of the invention,the central portion of the yolk must be at a temperature of 128° F. orhigher.

[0034] This means, of course, that when a heat transfer medium asdescribed above is used, that medium must be at a temperature of atleast 128° F., since, otherwise, that heating medium would not becapable of heating the central portion of the yolk to at least 128° F.On the other hand, while the central portion of the yolk should notreach a temperature greater than about 138.5° F., the temperature of theheating medium can be higher than that temperature, since there will bea temperature differential between the temperature of the heating mediumand the central portion of the yolk until an equilibrium temperature isestablished. However, it has also been found that a higher temperatureof the heating medium should not be substantially greater than 138.5°F., since, otherwise, the chances of decreasing the functionality of thealbumen before pasteurization occurs, especially near the shell,increases. For this reason, it is preferable that the medium is heatedto temperatures no greater than 142° F.

[0035] The medium may be heated to more than one temperature during thepasteurization process. For example, the medium may be heated to ahigher temperature of no greater than 142° F. for part of thepasteurization dwell time of the yolk, and then cooled to lowertemperatures no less than 128° F. for the remainder of the portion ofthe dwell time of the yolk. There are certain advantages to heating tosuch higher temperatures and then cooling to such lower temperaturesduring the pasteurization process, in that the total time required forpasteurization is decreased. At the higher yolk temperatures, withinparameter lines A and B of FIG. 1, the chances of decreased albumenfunctionality are increased. Therefore, in order to decrease processingtime and the chances of decreased functionality, the heating medium maybe heated to higher temperatures for part of the pasteurization and thenheated to a lower temperature for the remaining part of thepasteurization, consistent, of course, with the yolk temperature beingwithin the range specified above and within the dwell times of parameterlines A and B. If such different temperatures of the heating medium areused, it is preferable that the higher temperatures are between about136° F. and 139° F. and the lower temperatures are between about 131° F.and 135° F.

[0036] The most preferred method in the foregoing regard is that ofusing one or more higher heating medium temperatures, e.g. 138° F.,until the yolk temperature reaches a target value, e.g. 134° F., andthen decreasing the temperature of the medium to that targettemperature, e.g. 134° F., and maintaining that reduced mediumtemperature until the dwell time specified by FIG. 1 is reached. Severalor more different medium temperatures may be used, so long as theresulting temperatures and dwell times of the yolk fall within parameterlines A and B of FIG. 1. This provides some latitude in fine adjustmentof the process for optimum pasteurization and retention of functionalityof the egg even with varying egg input and input egg conditions.

[0037] In this latter regard, a difficult problem in the prior art,where the eggs were processed by temperature control of the heatingmedium alone, e.g. a water bath, for specified time ranges, is that theparticular input eggs and the prior handling conditions thereof couldvery substantially affect the results. For example, freshly laid eggsare normally stored in controlled temperature refrigerators untilhandling, processing, packaging and distribution are achieved, with thepossible exception of grading. However, such conditions are not uniform,and the conditions vary from processor to processor. Thus, if eggs to beprocessed according to the prior art were stored at 41° F. and thenplaced in a heated water bath maintained at the prescribed temperaturesand allowed to dwell therein for the prescribed time, the actual resultsthat would be achieved thereby in terms of decrease in microorganismsand preserved functionality would vary significantly from that whichwould be achieved if the eggs had been stored at, for example, 44° F.Those results would vary most considerably if the eggs to be processedwere brought to room temperature before processing. This is because theamount of heat required to be transferred into the egg to achievereduction in microorganisms depends upon the temperature of the eggentering the process, e.g. entering the temperature-controlled hot waterbath.

[0038] Likewise, the effects of specific dwell times in a water bathcontrolled at a specific temperatures will vary with the age of the egg.In addition, it will vary with the size, particular configuration,weight and density of the particular egg, which can vary somewhat. Atleast to some extent, the effects will vary with the particular breed ofpoultry used to produce the eggs.

[0039] All of these problems are obviated by the present method, wherethe control for pasteurization and retention of functionality is not inconnection, specifically, with the temperature of the heat transfermedium, but is the result of the control of the temperature of thecentral portion of the yolk of the egg.

[0040] However, changes in functionality, especially of the albumen, canoccur when the time required to reach the target yolk temperature withinparameter lines A and B is overly long. This is referred to as the“come-up” time. The “come-up” time can be minimized by prewarming theeggs, e.g. to room temperature or up to about 120° F., prior toprocessing for pasteurization. It should be noted that any time duringwhich the yolks of the eggs are within parameter lines A and B inreaching such target yolk temperature should be subtracted from thedwell time required by FIG. 1.

[0041] In regard to the “come-up” time, it was found that at yolktemperatures below 120° F., the growth rate of Salmonella is very low.Further, it was found that at yolk temperatures at 120° F. or below,protein denaturing (loss of functionality) also proceeds at a very lowrate. With these two discoveries, it was found that eggs could beprewarmed to yolk temperatures up to 120° F. over relative long timeswithout any significant increase in Salmonella or decrease infunctionality. While the longer the prewarming time the greater thechance for loss of functionality and increase in Salmonella, prewarmingperiods of up to two hours, especially one hour and more especially upto 30 minutes are quite satisfactory. Such prewarming can considerablyreduce the “come-up” time.

[0042] As noted above, the present method ensures that a Salmonellaspecies, which may be present in the egg yolk, is reduced by at least 5logs (base 10 log) while the albumen functionality of the egg, measuredin Haugh units, is not substantially less than the albumen functionalityof a corresponding unpasteurized in-shell egg. In this regard, it hasbeen found that if a Salmonella species present in the egg is reduced inan amount by at least 5 logs, then any other pathogenic microorganismwhich may be expected to be in the egg will also be reduced by at least5 logs, particularly, when the reduction of 5 logs is in connection withthe species Salmonella enteritidis. Salmonella enteritidis is aparticularly troublesome pathogenic species of Salmonella in that it isa more common species of infection in the yolk of the egg, for thereasons explained above, and is a particularly virulent pathogenicspecies. In addition, that species is more difficult to destroy becauseof its predominant yolk location and the corresponding difficulty todestroy while maintaining functionality. Therefore, if the process isdesigned and carried out so as to reduce Salmonella enteritidis by atleast 5 logs, as essentially the worst case scenario, then it can beassured that other pathogens in the egg have been reduced sufficientlythat the egg is safe for consumption by humans of ordinary health andcondition.

[0043] In this regard, FIG. 1 is a graph of the temperature of thecentral portion of the yolk of an egg being pasteurized versus the logof the dwell time of the yolk at that temperature. That correlation is astraight line on log scale, and parameter lines A and B show permissibledeviation from that correlation line, while still substantially ensuringa 5 log reduction in a Salmonella species, as well as a substantialretention of the albumen functionality. For optimum results, the dwelltime at a specific temperature or dwell times at different temperatures,as explained above, should fall near that correlation line. However, asnoted above, for some fine tuning of processes in connection with theparticular egg input, the technical ability to control temperatures, andfor shortening the process time, the time-temperature correlation can bewithin parameter lines A and B and satisfactory results will beobtained. However, it is much preferred that deviations from thecorrelation line be at longer dwell times, rather than at shorter dwelltimes, from the correlation line. This will ensure a 5 log reduction ofSalmonella while still ensuring good functionality. Thus, the dwelltimes are within a 95% statistical confidence level for the straightline graph of temperature and log of dwell time (indicated in minutes),where one terminus of the line is at 128° F. for 215 minutes and theother terminus of the line is at 138.5° F. for 8.0 minutes. The 95%confidence level is calculated by standard statistical methods which arewell known to the art and need not be described herein.

[0044] Thus, by carrying out the process so that the yolk is pasteurizedin the above manner, this also ensures that the entire mass of the eggis likewise pasteurized such that there is at least a 5 log reduction ofSalmonella species throughout the yolk, albumen and entire mass of theegg.

[0045] Newly proposed standards of the United States Food and DrugAdministration (USFDA) require at least a 5 log reduction in Salmonellaspecies for in-shell eggs to qualify as pasteurized. Acceptably retainedfunctionality must also be achieved for practical commercialapplication. Heretofore, the art has not been able to meet that proposedstandard. For example, only a 3 or 3.5 log reduction of a Salmonellaspecies could be achieved by prior art processes, while reliablyretaining the functionality of the in-shell eggs. As a result, some ofthe prior processes, instead, purported to use the USDA standard forliquid eggs (out-of-shell eggs). Those in-shell eggs are, nevertheless,not pasteurized eggs in that, while they may be safer to eat, they arenot safe to eat.

[0046] As noted above, while the functionality of an egg can bedetermined by several or more tests, it has been found that the mostsensitive and reliable test for determining retained functionality ofeggs pasteurized by the present invention is that of the albumenfunctionality test. Since the yolk temperature is controlled accordingto the present invention, i.e. controlled at a temperature between 128°F. and 138.5° F., this, inherently, means that the albumen reaches atemperature of at least 128° F., but could for a portion of the time ofthe pasteurization process reach temperatures up to 138.5° F. orslightly higher when the temperature of the heat transfer medium ishigher than 138.5° F., e.g. up to 142° F., as explained above.Therefore, these higher temperatures of the albumen, as opposed to thetemperatures of the yolk, can cause loss of functionality of the albumenbefore there is a substantial loss of functionality of the yolk. By,therefore, controlling the yolk temperature, the functionality of thealbumen is safeguarded so as to not be substantially reduced from thatof an unpasteurized egg. Therefore, it can be ensured that thefunctionality of the whole egg including the yolk will not besubstantially reduced in functionality.

[0047] As a very surprising and unexpected occurrence in connection withthe present invention, when pasteurization is carried out very close tothe correlation line of FIG. 1, not only is the albumen functionalitynot decreased but, in fact, quite surprisingly, is increased in someregards. The data actually shows that while a correspondingunpasteurized egg of Grade A quality may have an albumen functionalityrating of between 60 and 72 Haugh units, when an egg is pasteurizedclose to the present correlation line of FIG. 1, the albumenfunctionality rises by up to 10 units, e.g. somewhere in the 70 or 80units. It is noticed that there is a slight enlargement of the air sacand an enlargement of the yolk in such eggs, which enlargements areusually found in slightly older eggs. Even when operating the processclose to either parameter line A or parameter line B, the albumenfunctionality of pasteurized Grade A eggs will still exceed 60 Haughunits.

[0048] In this latter regard, the term “corresponding unpasteurizedin-shell egg” is defined to mean an egg of corresponding shape, weight,age, flock and processing history as that of the pasteurized egg, since,as explained above, these variables can effect the results of theprocess and, correspondingly, the results of the Haugh unit test.Therefore, in connection with the corresponding unpasteurized egg, thepasteurized egg is not substantially reduced in the albumenfunctionality test.

[0049] As is well known in the art, any substantial heating of eggprotein causes some denaturization of that protein. In the prior artprocesses, while reduction of microorganisms in the eggs could easily beachieved, reduction of higher log cycles resulted in denaturing of theegg protein and a decrease in the functionality of the eggs to theextent that the eggs were not commercially useful for all purposes. Inaddition, that denaturing of the protein causes very substantial changesin the functionality of the eggs with storage. Thus, in those prior artprocesses, while freshly heat-treated eggs might not have acceptablefunctionality for all uses, they might have acceptable functionality forlimited uses, e.g. producing a soft-boiled egg. However, with storage ofthe eggs, which is normal in the industry, even that functionality wouldsubstantially further decrease such that long time stored eggs wouldbecome unacceptable for almost all uses. Therefore, it is not onlynecessary to achieve pasteurization, while retaining functionality, asdescribed above, but it is also necessary to retain that functionalityover a significant period of time of storage of the eggs. Otherwise,without preservation of functionality during storage, the pasteurizedeggs are simply not acceptable from a commercial point of view.

[0050] Storage affects both unpasteurized and pasteurized eggs (e.g.stored at 41° F.). There is some weight loss during storage, the yolkheight and width tend to change, yielding a changed yolk index and thewhipped albumen height, in Haugh units, also tends to change in bothtypes. These are, however, usually not practically significant.Generally speaking, eggs should not be stored (e.g. at 41° F.) forlonger than about 75 days prior to use. In the prior art approaches, theprocessed eggs stored for up to 75 days showed unacceptable changes inegg functionality. For example, depending upon the prior art approach,the eggs could not make an acceptable sunny-side up fried egg,acceptable homogeneous scrambled eggs, or acceptable over-easy friedeggs. Neither could those eggs be used for making food products, such assalad dressings, e.g. Caesars salad dressing, mayonnaise, sponge cakes,cookies and other baking applications.

[0051] While the following example details the data of test results,that example shows that the present process not only destroys theSalmonella species so as to pasteurize the egg, i.e. at least a 5 logreduction, but does so without substantially adversely affecting the eggquality, e.g. functionality, even when stored up to 75 days at 41° F.Those eggs can be used for preparing sunny-side up, scrambled andover-easy cooked eggs, as well as in preparing salad dressings,mayonnaise, sponge cakes, cookies and other baking applications.

[0052] Thus, the present method and pasteurized eggs are furtherdifferent from prior art methods and treated eggs in that the presentpasteurized eggs have an egg weight substantially the same as acorresponding unpasteurized egg, a yolk index and yolk strengthsubstantially the same as a corresponding unpasteurized egg, and anangel cake test and a sponge cake test substantially the same as acorresponding unpasteurized egg. Further, the present pasteurized eggshave frying, scrambling and boiling characteristics substantially thesame as a corresponding unpasteurized egg, and, just as importantly,those characteristics are maintained in the present pasteurized eggs forup to 75-days storage at 41° F.

[0053] The egg produced by the method of the invention, as noted above,is a pasteurized in-shell chicken egg which comprises a pasteurizedcentral portion of the yolk of the egg having at least a 5 log reductionof a Salmonella species which may be present in the egg in itsunpasteurized form. The egg has an albumen functionality, measured inHaugh units, not substantially less than a corresponding unpasteurizedin-shell egg. In this regard, “not substantially less” means that anydifferences are not of practical significance. The present pasteurizedegg also has the reduction in Salmonella species throughout the yolk andalbumen of the egg. Also, the egg weight, the yolk index, the yolkstrength, the angel cake test, the sponge cake test, and frying,scrambling and boiling characteristics of the present pasteurized eggare not substantially less than a corresponding unpasteurized in-shellegg. Likewise, the present pasteurized egg can substantially maintainthose characteristics for up to 75-days storage at 41° F.

[0054] It will be appreciated by those skilled in the art that areduction in Salmonella species of at least 5 logs, while notsubstantially decreasing the albumen functionality, is a verysubstantial improvement in the art. Prior art approaches, such as thosedescribed above, under ideal conditions, could produce, perhaps, as muchas a 3.5 log reduction in Salmonella enteritidis without substantiallydecreasing the albumen functionality. However, while up to a 3.5 logreduction will make the egg safer to eat, that egg is not pasteurizedaccording to the proposed USFDA standard, discussed above, and, hence,cannot be said to be safely consumable by a human of normal health andcondition. Unless at least a 5 log reduction is obtained, under theproposed USFDA standard, it cannot be assured that the egg can be safelyconsumed by such human. The present process is able to achieve that 5log reduction, while maintaining the functionality of the egg, and, inthis sense, has solved the dilemma which has plagued the art for sometime. Indeed, by following closely the correlation line of FIG. 1, logreductions greater than 5 can be achieved, while substantiallymaintaining the functionality, e.g. 6 log reductions and even 7 logreductions, and this is a very substantial advance in the art.

[0055] While, as stated above, the method may be carried out by heatingthe eggs with any desired means, as also stated above, the preferredmethod is that of heating the eggs in an aqueous medium, preferably in awater bath, for the reasons set forth above, and this particular meansof heating the eggs will be specifically discussed, for concisenesspurposes, but it is to be understood that the invention is not limitedthereto. It should be further understood that the specific methodillustrated below is merely a preferred method when using a water bathas the heating medium, but that other methods may be used in connectionwith the use of a water bath as the heating medium, or in connectionwith other heat transfer media, so long as the yolk temperature/dwelltime of the invention is observed.

[0056] In carrying out the method, it is necessary to control the yolktemperature of the egg. However, it is first greatly preferred toappropriately calibrate a particular apparatus and particular processconditions of that apparatus to ensure that the particular apparatus andconditions calibration results in the required yolk temperature/dwelltime to pasteurize the eggs and retain functionality, according toFIG. 1. Thereafter, subsequent processing and pasteurization of eggs canbe achieved by repeating those calibration process conditions withoutmeasuring the yolk temperature/dwell time of the eggs. For example, insuch calibration, it may be established by temperature measurement ofthe yolk that when eggs stored at 41° F. are placed in a water bath at137° F. for a particular apparatus with a particular agitation for 14minutes and then removed and cooled in 41° F. storage, the yolktemperature/dwell time required by FIG. 1 is achieved. Thereafter, toeffect pasteurization of succeeding lots of eggs, including the requiredyolk temperature/dwell time and retained functionality, it is onlynecessary to maintain that calibration agitation, water temperature,14-minute dwell time, egg storage temperature and cooling temperature,to ensure that the yolk temperature/dwell time is that required by FIG.1, without having to measure that yolk temperature/dwell time orfunctionality of succeeding lots of eggs. However, it is preferable thatthe calibration be periodically rechecked during processing ofsucceeding lots of eggs by checking the calibration with a lot of eggsfrom time to time by measuring the temperature of the yolk and measuringfunctionality.

[0057] To these ends, for a chosen lot of eggs being pasteurized, astatistical number of the eggs being processed will have a temperatureprobe inserted into that central portion of the yolk, and these eggs maybe referred to as “control eggs”. The temperature probe, e.g.thermocouple, is inserted into the egg, in a manner well known in theart, and sealed thereagainst by conventional manners, e.g. glues, waxes,putties, and the like, to prevent water from entering the egg duringprocessing. The temperature of the central portion of the control eggyolks is monitored by the temperature probe, and the yolktemperature/dwell time is determined and controlled to ensure that thevalues fall within parameter lines A and B of FIG. 1. If so, thecalibration has been obtained or maintained; if not, adjustment ofoperating conditions and recalibration are required.

[0058] Whether in regard to such calibration or in regard to productionpasteurization of eggs, normally, eggs of essentially the same sizerange will be processed as a lot. Otherwise, with eggs of greatlydifferent sizes, the calibration or production processing could notensure pasteurization. The sizes may be determined by weight, and, forexample, eggs of a target weight plus or minus 10% are processed as alot.

[0059] In the method of the invention, a lot of eggs is placed in aconventional pasteurization apparatus, which may be any conventionalpasteurization apparatus, such as a cheese vat, and heated water isintroduced into that vat with the water being heated to at least 128° F.and up to 142° F., but preferably less than 138.5° F. The temperature ofthe central portion of the egg yolk of a statistical number of eggs ismonitored by a temperature probe present in “control” eggs as a periodicor continual recheck of calibration, as explained above, or as theprimary means of control of egg yolk temperature, e.g. in an apparatuswhich has not been calibrated as described above. Preferably, however,the apparatus has been calibrated, and such control eggs are notrequired or are used only periodically to recheck calibration. When thedesired target temperature of the yolk, e.g. 134° F. is reached, thetemperature of the water is controlled to maintain that targettemperature by adding cold or hot water as required, and that yolktemperature is controlled for the time set by the correlation line ofFIG. 1 or at least within parameter lines A and B.

[0060] After the eggs have reached that temperature and been controlledat that temperature for the time of the correlation line, the eggs areremoved from the pasteurizer and cooled to at least below 126° F., andmore preferably below 115° F., and yet more preferably below 100° F.This cooling should be as rapid as possible such that residualtemperatures in the eggs do not substantially further denature proteinbeyond that achieved at the correlation temperature. Usual coolingprocedure, e.g. air, is sufficient for this purpose, but it ispreferable to cool the eggs in cool water or in normal storage, e.g 41°F., after removal from the pasteurizer. It should be noted that any timeduring which the yolks of the eggs remain within parameter lines A and Bduring cooling should be subtracted from the dwell time required byFIG. 1. After the eggs have been so cooled, the eggs are then dried,e.g. air drying, packaged and transferred to a cold storage, maintainedat an acceptable temperature of between 38° F. and 45° F., e.g. 41° F.,and are then ready for distribution.

[0061] In addition, for calibration, recheck of calibration or primarycontrol of the pasteurization, a statistical number of “control” eggsmay be analyzed for functionality. While the functionality will belargely known by the albumen functionality test, in Haugh units, toensure that the functionality of the pasteurized egg is substantiallythe same as a corresponding unpasteurized egg, in addition to thealbumen functionality, “control” eggs may be examined for egg weight,yolk index and yolk strength, angel cake test and sponge cake test, aswell as the characteristics of frying, scrambling and boiling, asdescribed above.

[0062] All of the control eggs, i.e. yolk temperature and functionalitycontrol eggs, are essentially part of calibration for a particularpasteurizing apparatus operated at particular conditions with particulareggs. This is because particular pasteurizing apparatuses can vary intheir performance of pasteurization, and any particular apparatus mustbe calibrated to ensure that the yolk temperature/dwell time reaches thedesired results required by FIG. 1. However, as noted above, oncecalibrated, for successive pasteurizations of substantially the sameeggs, then it is no longer necessary to use the temperature probed“control” eggs or to perform the functionality tests mentioned above,since by repeating the calibration process, the same results will beachieved. This is, of course, based on the assumption that allsucceeding lots of eggs processed in that same manner have essentiallythe same histories and conditions, as described above. If the historiesor conditions change markedly, then the apparatus must be recalibrated,as discussed above.

[0063] Optionally, the pasteurized eggs may be protected fromenvironmental recontamination by wrapping the eggs or cartons of eggs ina protective barrier, such as a plastic film. Heat shrinkable plasticfilm is particularly well suited to this purpose, such as the heatshrinkable films made by the Cryovac Division of W. R. Grace & Co. Thesefilms are co-extruded polyolefin films, some of which are cross-linked.These films are generally referred to as “industrial food source films”and particularly useful are those films designed as D-955 and MPD 2055.It is to be understood, however, that pasteurization of eggs, similar topasteurization of milk, does not extend the shelf life of the eggs nordoes it lessen the necessity for proper handling and cooling of theeggs, in the same manner as pasteurized milk. Accordingly, simplywrapping each individual egg or package of eggs will not extend theshelf life of the eggs.

[0064] The invention will now be illustrated by the following example,where all percentages and parts are by weight, unless otherwiseindicated.

EXAMPLE

[0065] This example illustrates two different protocols for pasteurizingeggs.

[0066] In a manner described above in connection with the method ofcalibrating a particular apparatus/process conditions, the graph of FIG.1 was experimentally determined by inoculating a statistical number ofeggs with Salmonella enteritidis. The inoculated eggs were sealed in thesame manner as sealing the temperature probe of the “control” eggs.These “control” inoculated eggs were processed in the same manner. The“control” inoculated eggs were examined for Salmonella enteritidis logreduction by standard microbiological techniques. The graph of FIG. 1was then constructed on the basis of yolk temperature/dwell time whichwould achieve at least a 5 log reduction in Salmonella enteritidis.Parameter lines A and B show a 95% confidence level. Retainedfunctionality was confirmed by the same procedure described below.

[0067] Thus, it was known by this experimental data that by processingeggs within parameter lines A and B of FIG. 1, a 5 log reduction in aSalmonella species resulted while maintaining functionality. ThisExample, therefore, illustrates that retained functionality and furtherillustrates that retained functionality during long-term storage, i.e.at 41° F. for up to 75-days storage.

[0068] The pasteurizer used in this example was a Kusel (Kusel EquipmentCo., Watertown, Wis.). It has a 100 gallon capacity and is usually usedas a cheese vat. The vat is filled with water and heated to the targettemperature with a steam jacket. The vat is equipped with a Nonoxsteam/water mixer and that target temperature is maintained by flowingtemperature controlled water into the vat with a corresponding outflowof water. For temperature control, the vat is equipped with mountingsfor separate temperature probes to monitor the water temperature. Inthis example, the water temperature was monitored using three Type T 24gauge (copper-constantant Teflon-coated) thermocouples connected to aCole-Palmer (Niles, Ill.) Dual Input Thermocouple Thermometers (ModelNo. 08112-20). The thermocouples were placed at three differentlocations and at three different water levels throughout the vat tomonitor the evenness of water temperature.

[0069] Thirty-six eggs were used in each test and were placed inconventional filler flats at 12 inches below the water level. Each batchof test eggs also contained three eggs that were probed with athermocouple. The thermocouple was inserted 1-¾ inches into the largeend of the eggs to the central portion of the yolks. The eggs weresealed with a gel-based glue and allowed to dry. Temperatures of theeggs and water vat were monitored at one minute intervals with anaccuracy of ±0.2° F. Mild agitation was carried out in the vat and wasregulated using a rotary stainless steel impeller pump with a 1-½ inchinlet and a 1-½ inch outlet.

[0070] Approximately 4-day old eggs were used for each of the tests, andthe eggs were large Grade A quality eggs from the same flock. The eggshad been stored at 41° F. until processed. The eggs were removed fromthe storage cooler and placed into the plastic filler flats. The threeeggs with the thermocouples mounted therein were also included in eachflat. The filler flat was then placed in the preheated vat, and thetemperatures of the water and the egg yolk temperatures were recorded atone minute intervals.

[0071] In one protocol, when the average internal yolk temperature ofthe three eggs reached 134° F., cool water was added to the vat andmixed, as needed, to maintain that internal yolk temperature. In theother protocol, the cool water was added when the average internaltemperature of the yolk reached 133° F. Both of the protocol fall withinparameter lines A and B of FIG. 1.

[0072] After processing, the eggs were removed from the water vat andplaced directly into a 41° F. cooler, by which they were rapidly cooled.

[0073] No pasteurized eggs were removed from the cooler until after theaverage internal yolk temperature reached 41° F. The various batches foreach treatment were combined and randomly assigned to Day 0, 10, 20, 30,60 or 75 days storage.

[0074] Treatment of the eggs were assigned treatment numbers as follows:

[0075] 1. Treatment No. 1—a control group of unpasteurized eggs;

[0076] 2. Treatment No. 2—a control group of unpasteurized eggs whichwere placed in a Cryovac package (film);

[0077] 3. Treatment No. 3—pasteurized eggs, initial water bathtemperature of 137° F. and average internal yolk temperature of 133° F.;

[0078] 4. Treatment No. 4—pasteurized eggs, initial water bathtemperature of 137° F. and average internal yolk temperature of 133° F.,packaged within a Cryovac package;

[0079] 5. Treatment No. 5—pasteurized eggs, initial water bathtemperature of 138° F. and average internal yolk temperature of 134° F.;and

[0080] 6. Treatment No. 6—pasteurized eggs, initial water bathtemperature of 138° F. and average internal yolk temperature of 134° F.,packaged within a Cryovac package.

[0081] Treatment Nos. 2, 4 and 6 were packaged in groups of six incardboard or plastic filler flats. The packaging was provided by Cryovacand consisted of a plastic sleeve into which the eggs were placed andthen sealed using a bar sealer. The plastic sleeve was made of CryovacD-955 film.

[0082] A description of the tests of the various treatments at dayintervals is set forth in Table 1 below. TABLE 1 Day Treatment Tests  0#1, #3, #5 Egg Quality - Weight Yolk Index Haugh Units Yolk StrengthFoam Stability Angel Cake Volume Sponge Cake Volume Whip Test LysozymeActivity 10 & 20 #1, #2, #3, Egg Quality - Weight #4, #5, #6 Yolk IndexHaugh Units Yolk Strength 30, 60 & 75 #1, #2, #3, Egg Quality - Weight#4, #5, #6 Yolk Index Haugh Units Yolk Strength Foam Stability AngelCake Volume Sponge Cake Volume Whip Test Lysozyme Activity

[0083] A. Egg Quality Tests:

[0084] 1. Egg Weight—Initial and final egg weights (to one hundredth ofa gram) were recorded to determine if a weight gain or loss occurredduring processing or storage.

[0085] 2. Yolk Index—Yolk index is a measure of yolk quality. Adecreasing yolk index indicates a lower yolk quality.${{Yolk}\quad {index}} = \frac{{Yolk}\quad {height}\quad ({mm})}{{Yolk}\quad {width}\quad ({mm})}$

[0086] 3. Haugh Units (Albumen Functionality Test)—The Haugh unitsmeasure albumen (egg white) quality. As the egg ages, the thick whitethins. The Haugh units are calculated using both the egg weight and theheight of the thick albumen. Standard Haugh unit values for differentgrades of eggs are as follows: Grade AA >72 Haugh units Grade A 60-72Haugh units Grade B <60 Haugh units

[0087] 4. Yolk Strength—Yolk strength is a measure of how easily theyolk will break when dropped from a distance of 6 inches onto a flatsurface.

[0088] B. Properties Tests:

[0089] 1. Angel Cake Volume—Angel cake volume is a sensitive test of eggwhite protein damage. Generally, heat damage will greatly increasewhipping time and decrease the cake volume.

[0090] 2. Sponge Cake Volume—Measures both foaming volume andemulsification properties. The yolk proteins are less heat sensitivethan egg white proteins. Sponge cake volume provides a measure of theeffect of heat processing on yolk functionality.

[0091] 3. Foaming Stability—Measures the foaming efficiency of eggwhites. The foaming properties of egg whites are provided by certain eggwhite proteins. These proteins are particularly sensitive and may bedamaged by heat processing. If proteins are damaged, then foam volumewill decrease and the liquid drainage from the whipped foam willincrease. The egg whites are whipped to a specific gravity of 0.1.Percent drainage was calculated by dividing the grams of drainage by theinitial weight of the foam.

[0092] 4. Whip Test—This is another measure of the foaming efficiency ofegg whites. Egg whites are whipped for a specific time and speed and theheight of the foam is then measured.

[0093] All functionality tests were performed in triplicate pertreatment.

[0094] C. Other Tests:

[0095] 1. Lysozyme Test—This test measures the enzyme activity. Lysozymeis one of the constituents in eggs which provides some antibacterialactivity. It acts upon gram positive organisms. Rate of clearing wasdetermined per minute at the most linear portion of the curve, i.e.between 0.5-3.0 minutes.

[0096] Results and Observations of Eggs at Day 0

[0097] Visual Observations

[0098] Observations were conducted on eggs from Treatment Nos. 1, 3 and5. Treatment No. 1 (unpasteurized eggs) showed no signs of cloudiness,and the yolk shape was normal. Treatment No. 3, pasteurized with aninitial water bath temperature of 137° F. and a yolk temperature of 133°F. (137-133° F.) showed cloudiness in the thick and thin albumen. Theyolk was slightly flatter than in Treatment No. 1. Treatment No. 5(138-134° F.) was very similar in appearance to Treatment No. 3, withthe exception of a slight decrease in cloudiness in the thin albumen.

[0099] Egg Quality

[0100] Weight Loss—No statistically significant (p>0.05) differences inweight loss occurred between the control and pasteurized eggs at Day 0.A statistically significant (p<0.05) difference was found between thepasteurized eggs, with the eggs from Treatment No. 3 (137-133° F.)losing the least amount of weight.

[0101] Yolk Index—No statistically significant (p>0.05) differences inyolk index occurred between Treatment Nos. 1, 3 and 5.

[0102] Yolk Strength—Pasteurization did not statistically significantly(p>0.05) affect yolk strength.

[0103] Haugh Units—No statistically significant (p>0.05) differences inHaugh units occurred between Treatment Nos. 1, 3 and 5.

[0104] Properties Test

[0105] Angel Cake Volume—Differences in angel cake volume between allthree treatments were not statistically significant (p>0.05). However,whipping time to achieve a medium peak was increased in the pasteurizedeggs compared to the control eggs.

[0106] Sponge Cake Volume—Significant (p<0.05) differences were found insponge cake volume between Treatment Nos. 3 and 5, with Treatment No. 3having greater cake volume. There was not a statistically significant(p>0.05) difference in sponge cake volume between the control andpasteurized eggs.

[0107] Whip Test—Whip test results indicated a statistically significant(p<0.05) difference between the control and pasteurized eggs with thecontrol eggs having the least amount of drainage and the greatest foamvolume. There was no statistically significant (p>0.05) differencebetween Treatment Nos. 3 and 5. To achieve a specific gravity of 0.1 inthe control eggs, the whipping time was 30 seconds compared to 3 minutesfor the pasteurized eggs.

[0108] Other Tests

[0109] Lysozyme—A statistically significant (p<0.05) difference inlysozyme activity was found between the control and pasteurized eggs.Differences in enzyme activity between Treatment Nos. 3 and 5 were notstatistically significant (p>0.05).

[0110] Conclusion

[0111] At Day 0, the pasteurized eggs exhibited some cloudiness in thethick albumen (white) as compared to unpasteurized eggs. The degree ofcloudiness is not practically significant.

[0112] A small amount of weight was lost during the pasteurizationprocess but was comparable to average weight loss in the unpasteurizedeggs. No weight gain occurred during pasteurization. The pasteurizationprocess did not practically significantly adversely affect the yolkindex, Haugh units, or yolk strength. After pasteurization, the eggsremained large Grade A quality eggs.

[0113] Pasteurization did not practically significantly affect angel andsponge cake volume when comparing to the unpasteurized egg. However,Treatment No. 3 (137-133° F.) had a greater sponge cake volume thanTreatment No. 5 (138-134° F.), which was found to be significant.

[0114] Unpasteurized eggs were slightly superior in foam volume and foamstability as compared to the pasteurized eggs, but this superiority isnot practically significant.

[0115] Lysozyme activity decreased in the pasteurized eggs as comparedto the unpasteurized eggs. However, the loss in activity is of littlepractical significance.

[0116] Results and Observations of Eggs at Day 10

[0117] At Day 10, the results were similar to Day 0 in regard to thecommon tests. Cloudiness was apparent in the pasteurized eggs comparedto the unpasteurized eggs. The degree of cloudiness is not practicallysignificant. No visual differences were observed between the packagedand unpackaged eggs.

[0118] Some degree of weight loss occurred in all treatments during the10-day storage period. Packaging did not significantly affect the amountof weight loss.

[0119] A statistically significant difference was found in yolk indexbetween the pasteurized and unpasteurized eggs and the packaged andunpackaged eggs. Haugh units were not affected by the pasteurizationprocess. Unpackaged eggs had higher Haugh units as well as eggs fromTreatment Nos. 5 and 6. The differences in the yolk index and Haughunits are not practically significant and do not affect the quality ofthe eggs. The eggs were still large Grade A quality eggs.

[0120] Results and Observations of Eggs at Day 20

[0121] At Day 20, the results were similar to Day 10 in regard to thecommon tests. The pasteurized eggs at Day 20 were still cloudy inappearance as compared to the unpasteurized eggs. Some cloudiness alsoappeared in the thin albumen. The degree of cloudiness is notpractically significant. Packaging did not affect the visual appearanceof the eggs.

[0122] All treatments lost weight at Day 20 of storage. Packaging diddecrease the amount of weight loss as compared to the unpackaged eggs.The unpasteurized eggs lost less weight compared to the pasteurizedeggs. The amount of weight loss is not practically significant and wouldnot change the grade designation.

[0123] The unpasteurized eggs had a slightly higher yolk index.Packaging did not affect yolk index. No practical significantdifferences in Haugh units or yolk strength were apparent between alltreatments. At the end of 20-days storage, all eggs were still largeGrade A quality eggs.

[0124] Results and Observations of Eggs at Day 30

[0125] At Day 30, the results were similar to Day 20 in regard to thecommon tests. Cloudiness in the thick albumen and slight cloudiness inthe thin albumen were present in the pasteurized eggs. The pasteurizedeggs were also slightly more runny in the outer thin albumen thanunpasteurized eggs. No differences between the packaged and unpackagedeggs were apparent. The degree of cloudiness and runniness is notpractically significant.

[0126] Weight loss occurred in all treatments, with the unpasteurizedeggs losing the least amount of weight. Packaging did not have asignificant effect on weight loss. Unpackaged eggs had a higher yolkindex than those that were packaged. Packaging and pasteurization didnot have a significant effect on yolk strength or Haugh units. The eggsstill remained large Grade A quality eggs after 30 days of storage.

[0127] Angel cake and sponge cake volume was not affected in alltreatments at Day 30. Longer whipping times were necessary for thepasteurized eggs. Packaged and pasteurized eggs had a greater spongecake volume but were not practically superior to the other treatments.

[0128] Foam stability and volume were greatest in the unpasteurizedeggs. Longer whipping times were necessary in the pasteurized eggs. Lossof lysozyme activity occurred in all treatments; however, the loss inactivity is of little practical significance. None of these differenceswere of practical significance.

[0129] Results and Observations of Eggs at Day 60

[0130] At Day 60, the results were similar to Day 30. The cloudiness ofthe thick albumen and slight cloudiness in the thin albumen of thepasteurized eggs were observed. Packaging did not play a significantrole in appearance. The outer thin albumen of pasteurized eggs wasslightly more runny than the unpasteurized eggs. The degree ofcloudiness and runniness of the pasteurized eggs is not practicallysignificant.

[0131] Weight loss occurred in all treatments but was not significantlyaffected by packaging or heat treatments. Weight loss was notsignificant enough to change the classification of the eggs.

[0132] Yolk strength and yolk index were not affected by pasteurizationor packaging. Haugh units were greater in pasteurized eggs thanunpasteurized eggs. At the end of 60-days storage, all treated eggs werestill large Grade A quality eggs.

[0133] Unpasteurized eggs had greater angel and sponge cake volume.Packaging did not play a significant role in cake volume. Foam stabilityand volume were greater in the unpasteurized eggs. Longer whipping timeswere needed for the pasteurized eggs. None of these differences werepractically significant.

[0134] Lysozyme activity was lost in all treatments but was notpractically significant.

[0135] Results and Observations of Eggs at Day 75

[0136] At Day 75, the results were similar to Day 60. The pasteurizedegg albumen was more cloudy than that of unpasteurized eggs. The degreeof cloudiness is not practically significant. Runniness was moreapparent in the outer thin albumen. Packaging did not appear to make asignificant difference in egg quality.

[0137] Weight loss occurred in all treatments, with the packaged eggslosing the least amount of weight. Yolk index was better in theunpasteurized eggs. Yolk strength was not significantly affected bypasteurization or packaging. Haugh units were greater in the pasteurizedeggs than in the unpasteurized eggs. However, at the end of Day 75, alltreatments were still large Grade A quality.

[0138] Angel cake volume was not significantly affected bypasteurization or packaging. Unpasteurized and unpackaged eggs had thegreater sponge cake volume. None of these differences are of practicalsignificance.

[0139] Foam stability and volume were superior in the unpasteurized eggscompared to pasteurized eggs. Longer whipping times were required forthe pasteurized eggs. None of these differences were of practicalsignificance.

[0140] Lysozyme activity decreased in all treatments after 75 days ofstorage, but not enough to cause a practical significant effect.

[0141] Overall Conclusion

[0142] Cloudiness of the thick albumen occurs in pasteurized eggs thatis not apparent in the unpasteurized eggs. However, the degree ofcloudiness is not practically significant. Cloudiness remainedessentially constant during the 75-day test period and is similar to thenatural cloudiness of two-day old eggs.

[0143] Weight loss statistically significantly (p<0.05) increased duringstorage for all treatments. Packaging statistically significantly(p<0.05) reduced weight loss of all three treatment groups. Pasteurizedeggs were noted to have statistically significantly (p<0.05) more weightloss as compared to unpasteurized eggs. None of these differences,however, are of practical significance.

[0144] Yolk index of the control eggs was found to be statisticallysignificantly (p<0.05) better than the pasteurized eggs for most of thestorage periods. Yolk index statistically significantly (p<0.05)declined in all groups up to 60 days. All treatments exhibited anincrease in yolk index at 75 days, which resulted in a statisticallysignificant (p<0.05) day by treatment interaction. This increase is,however, not practically significant.

[0145] The yolk breakage test indicated that yolk breakage wassatisfactory in all groups throughout the storage study.

[0146] Haugh units of pasteurized eggs were observed to be statisticallysignificantly (p<0.05) higher than the control eggs. This wasparticularly true at longer storage periods (beyond 30 days). Packagingstatistically significantly (p<0.05) improved the Haugh units of alltreatment groups.

[0147] Angel cake volume was found to be variable. Control eggs werefound to have a statistically significantly (p<0.05) better angel cakevolume. Whip foam volume and foam stability were statisticallysignificantly (p<0.05) superior in control eggs as compared topasteurized eggs. None of these differences are, however, practicallysignificant.

[0148] Sponge cake volume was statistically significantly (p<0.05)better in pasteurized eggs up to 30 days as compared to control eggs.After 30 days, the control group eggs were noted to have statisticallysignificantly (p<0.05) better sponge cake volume. The 137° F. treatmentgroups eggs were found to have a statistically significantly (p<0.05)better sponge cake volume as compared to the 138° F. treatment group.Although sponge cake volume was variable and declined through storage,the sponge cake volume was acceptable in all tests, and the differencesare not practically significant.

[0149] Lysozyme activity statistically significantly (p<0.05) declinedin all treatment groups throughout storage. Pasteurization alsostatistically significantly (p<0.05) reduced lysozyme activity. Previousresearch has shown that lysozyme activity in shell eggs will decreaseduring storage. Although lysozyme activity was lower in pasteurizedeggs, this difference is not practically significant.

[0150] The pasteurized eggs are suitable for all forms of foodpreparation. They can be prepared sunny-side up, scrambled andover-easy. The pasteurized eggs can also be utilized in salad dressings(e.g. Caesars salad), mayonnaise, sponge cakes, cookies and other bakingapplications.

[0151] Thus, overall, there was no practical significant difference infunctionality of the pasteurized eggs as compared with correspondingunpasteurized eggs for the entire storage period. Test Details SpongeCake Test Ingredients: 50.0 g cake flour 46.25 g sucrose 19.30 gdextrose 5.0 g nonfat dry milk 1.25 g salt 2.50 g baking powder 29.49 gwhole egg 18.90 g water (first addition) 10.26 g water (second addition)

[0152] Procedure:

[0153] 1. Preheat oven to 375° F.

[0154] 2. Allow all ingredients to come to room temperature.

[0155] 3. Sift all dry ingredients.

[0156] 4. Blend all dry ingredients for one minute on the stir speed ofa Kitchen Aid Mixer (Model K4-B).

[0157] 5. Add egg to mixture.

[0158] 6. Mix for 1 minute at speed 2 while slowly adding the firstwater.

[0159] 7. Scrape down sides of bowl.

[0160] 8. Mix for 2 minutes at speed 8.

[0161] 9. Mix for 2 minutes at speed 4, while slowly adding the secondwater.

[0162] 10. Scrape down sides of bowl.

[0163] 11. Mix 2 minutes at speed 8.

[0164] 12. Measure out 150 g into a tared 5.5″×3.5″×2.75″ baking pan.(Two 1″ strips of wax paper placed lengthwise along the bottom of thepan, extended over the ends to facilitate removal of the cake from thepan.)

[0165] 13. Bake in reel-oven for 30 minutes.

[0166] 14. After baking, allow to cool for 10 minutes, and remove frompan.

[0167] 15. Volume determinations are made with a rape seed displacementmethod. Record initial volume of rape seeds. Turn mechanism over and addcake. Invert mechanism to allow rape seeds to surround cake and recordfinal volume.

[0168] 16. Report results as cm³. Angel Cake Test Ingredients: 90.0 mlblended egg white 1.8 g salt-cream of tartar mixture (0.45 g salt, 1.35g cream of tartar) 69.0 g super-fine sugar 56.0 g flour-sugar mixture(23.0 g sugar, 33.0 g flour)

[0169] Procedure:

[0170] 1. Preheat oven to 390° F.

[0171] 2. Warm Kitchen Aid Mixer (Model K4-B) by letting it run at speed10 for 15 minutes.

[0172] 3. Sift twice, separately:

[0173] 56.0 g flour-sugar mixture

[0174] 69.0 g sugar

[0175] 1.8 g salt-cream of tartar mixture

[0176] 4. Place 90.0 ml blended egg white in a bowl, sift salt-cream oftartar mixture over egg white.

[0177] 5. With mixer set on speed 10, white to a medium peak.

[0178] 6. Sift 69.0 g super-fine sugar over foam in three increasinglylarger portions and whip at speed 6 for 4 seconds after each addition.

[0179] 7. Sift 56.0 g of flour-sugar mixture onto foam in 3 portions,folding after each addition. Use a wire whip and about 20 strokes.

[0180] 8. Weight out 120 g of the batter into a tared 5.5″×3.5″×2.75″pan (two 1″ strips of wax paper placed lengthwise along the bottom ofthe pan, extended over the ends to facilitate removal of the cake fromthe pan) with perpendicular sides. Place in reel oven for 20 minutes.

[0181] 9. Remove from the oven and place in an inverted position on acooling rack.

[0182] 10. After 24 hours, measure and record cake volume, using therape seed displacement method. Record initial volume of rape seeds. Turnmechanism over and add cake. Invert mechanism to allow rape seeds tosurround cake and record final volume.

[0183] 11. Report results as cm³.

[0184] Foaming Stability Test

[0185] Procedure:

[0186] 1. Weigh out 50 gram sample of room temperature egg white. Placein mixing bowl (Kitchen Aid Mixer, Model K4-B). Add 10 ml of distilledwater.

[0187] 2. Begin timing and whip at high speed (speed 10) until the foamhas a specific gravity of approximately 0.1. Specific gravitydetermination: density determination is substituted, tare a container ofknown volume, fill, level and weigh. Density is determined by: Weight ingrams = Density Volume in ml

[0188] The whipping time for this stage to be reached is noted.

[0189] 3. Transfer the foam to a tared glass funnel and immediatelyrecord weight of the foam.

[0190] 4. Cover the funnel with a large petri plate and allow to draininto a graduated cylinder tared on a scale.

[0191] 5. Record weight of drainage at 15 minute intervals for 1 hour.

[0192] Calculation: Calculate grams of drainage per 100 grams of foamfrom the total weight of foam and the weight of drainage by:${\frac{{Grams}\quad {of}\quad {Drainage}}{{Grams}\quad {of}\quad {foam}} \times 100} = {\% \quad {Drainage}}$

[0193] Whipping Test

[0194] Procedure:

[0195] 1. Weigh out 50 gram sample of room temperature egg white. Placeinto mixing bowl (Kitchen Aid Mixer, Model K4-B).

[0196] 2. Mix for 90 seconds on speed 2.

[0197] 3. Mix for 90 seconds on speed 10.

[0198] 4. Transfer foam from bowl into 600 ml beaker. Level foam andmeasure depth of foam.

[0199] 5. Record results in cm. Lysozyme Assay Reagents: 0.0667 M SodiumPhosphate Monobasic: Dissolve 9.218 g NaH₂(PO₄) H₂O and bring to 1 Lfinal volume. 0.0067 M Sodium Phosphate Dibasic: Dissolve 9.48 g Na₂HPO₄and bring to 1 L final volume. M/15 Phosphate Buffer pH 6.2: Mixportions of 0.0667 M Sodium Phosphate Mono and Dibasic solutionstogether until a pH 6.2 is reached. About 300 ml of dibasic to 1 Lmonobasic. 50 mg % Suspension of U.V. Killed and Lyophilized MicrococcusLysodeikticus: Dissolve 0.5 g in M/15 phosphate buffer pH 6.2 and bringto 1 L final volume. Keep refrigerated at 4° C.

[0200] Procedure:

[0201] Allow preblended egg white samples and cell suspension to come toroom temperature. Use plastic as lysozyme adheres to glass.

[0202] Dilute egg white samples to give a moderate clearing rate. Add0.02 ml of egg white to 0.98 ml buffer, gives a theoretical lysozymeconcentration of 70 ug/ml, the limits of this assay are 0.1 to 10 ug(per 2.9 ml substrate) of active lysozyme.

[0203] Using the kinetics software package on a BeckmanSpectrophotometer, edit program to the following:

[0204] Wavelength=450 nm

[0205] Tabulate=1.0 (yes)

[0206] Int Time=3.00 sec

[0207] Total Time=8.00 min

[0208] Plot=1.0

[0209] Span=0

[0210] Slope=1

[0211] Results=1

[0212] Factor=1.000

[0213] Calibrate using 2.9 ml of cell suspension.

[0214] Place cuvette containing 2.9 ml of 50 mg % cell suspension intocell holder in spectrophotometer. Add 0.1 ml of diluted egg white andimmediately mix using a plastic pasteur pipet. Allow program to run.

[0215] Maximum velocity will be extrapolated from the most linearportion of the curve by the software package. Factors used are 2-8 min.,2-4 min, 3-8 min., and 0.5-3 minutes. Rate reported per minute bysoftware.

[0216] Report as delta abs (at 450 nm)/min. per g sample/2.9 mlsubstrate at 22° C. (room temperature).

[0217] From the above example, it can be seen that the inventionprovides a method for, and a pasteurized egg resulting therefrom,reducing a Salmonella species that may be present in eggs by at least 5logs, while at the same time does not substantially practically decreasethe functionality of the pasteurized egg. This is a most significantadvance in the art. From the foregoing, it will be understood that theterm “pasteurized” in connection with the present invention means that aSalmonella species which may be present in a chicken egg is reduced byat least 5 logs, the pasteurized egg is safe for consumption by humansof ordinary health and condition, and the functionality of the egg,measured in Haugh units, is not substantially less than that of acorresponding unpasteurized chicken egg. In this latter regard, the term“substantially less” does not mean there is no statistically significantdifference, but means that there is no practical difference in terms ofusual uses of the eggs, e.g. in baking, cooking, frying, boiling,poaching, scrambling, etc. The specification and claims should thus beso construed.

[0218] It also should be understood that the invention is not limited tothe foregoing embodiments, but extends to the spirit and scope of theannexed claims.

What is claimed is:
 1. A method of pasteurizing an in-shell chicken egg,comprising heating the egg until a temperature of a central portion of ayolk of the egg is controlled within the range of 128° F. to 138.5° F.and maintaining that controlled yolk temperature for times withinparameter line A and parameter line B of FIG. 1 and sufficient that aSalmonella species present in the egg yolk is reduced in amount by atleast 5 logs but insufficient that an albumen functionality of the eggmeasured in Haugh units is substantially less than the albumenfunctionality of a corresponding unpasteurized in-shell chicken egg. 2.The method of claim 1, wherein the egg is heated with a fluid heattransfer medium.
 3. The method of claim 2, wherein the medium is anaqueous medium.
 4. The method of claim 3, wherein the aqueous medium isliquid water.
 5. The method of claim 4, wherein the water contains asurface active agent.
 6. The method of claim 4, wherein at least one ofthe water and the egg is in motion relative to the other.
 7. The methodof claim 2, wherein the medium is heated to temperatures of at least128° F.
 8. The method of claim 7, wherein the medium is heated totemperatures of at least 128° F. and up to 142° F. and the centralportion of the yolk is controlled at a temperature of at least 128° F.9. The method of claim 8, wherein the medium is heated to more than onetemperature.
 10. The method of claim 9, wherein the medium is heated toa higher temperature of less than 142° F. and then cooled to a lowertemperature greater than 128° F.
 11. The method of claim 10, wherein thehigher temperature is between about 136° F. and 138° F. and the lowertemperature is between about 131° F. and 135° F.
 12. The method of claim1, wherein said times are within a 95% confidence interval for astraight line graph of temperature and the log of dwell time in minuteswhere one terminus of the line is at 128° F. for 215 minutes and theother terminus of the line is at 138.5° F. for 8.0 minutes.
 13. Themethod of claim 1, wherein the Salmonella species is Salmonellaenteritidis.
 14. The method of claim 1, wherein the albumenfunctionality is at least 60 Haugh units for Grade A eggs.
 15. Themethod of claim 1, wherein the Salmonella species is reduced throughoutthe yolk and albumen of the egg by at least 5 logs.
 16. The method ofclaim 1, wherein the pasteurized egg has an egg weight substantially thesame as a corresponding unpasteurized egg.
 17. The method of claim 16,wherein the pasteurized egg has a yolk index and yolk strengthsubstantially the same as a corresponding unpasteurized egg.
 18. Themethod of claim 17, wherein the pasteurized egg has an angel cake testand sponge cake test substantially the same as a correspondingunpasteurized egg.
 19. The method of claim 18, wherein the pasteurizedegg has frying, scrambling and boiling characteristics substantially thesame as a corresponding unpasteurized egg.
 20. The method of claim 19,wherein said characteristics are maintained in the pasteurized egg forup to 75 days storage at 41° F.
 21. A pasteurized in-shell chicken egg,comprising a pasteurized central portion of a yolk of the egg having atleast a 5 log reduction in a Salmonella species present in the yolk inits unpasteurized form, said egg having an albumen functionalitymeasured in Haugh units not substantially less than the albumenfunctionality of a corresponding unpasteurized in-shell egg.
 22. The eggof claim 21, wherein the Salmonella species is Salmonella enteritidis.23. The egg of claim 21, wherein the albumen functionality is at least60 Haugh units for a Grade A egg.
 24. The egg of claim 21, wherein theSalmonella species is reduced throughout the yolk and albumen of the eggby at least 5 logs.
 25. The egg of claim 21, wherein the pasteurized egghas an egg weight substantially the same as a correspondingunpasteurized egg.
 26. The egg of claim 25, wherein the pasteurized egghas a yolk index and yolk strength substantially the same as acorresponding unpasteurized egg.
 27. The egg of claim 26, wherein thepasteurized egg has an angel cake test and sponge cake testsubstantially the same as a corresponding unpasteurized egg.
 28. The eggof claim 27, wherein the pasteurized egg has frying, scrambling andboiling characteristics substantially the same as a correspondingunpasteurized egg.
 29. The egg of claim 28, wherein said characteristicsare maintained in the pasteurized egg for up to 75 days storage at 410°F.